1. Field of the Invention
This invention relates to a rotary slide valve for auxiliary power steering systems in motor vehicles. The rotary slide valve contains two valve elements that are arranged so that they are coaxially movable inside each other and so that they can be turned by a maximum of the turning distance of a dead-travel clutch with respect to each other. The first valve element is connected in a non-rotary manner with a valve inlet member and the second valve element is connected with a valve outlet member via a dead-travel clutch. The first valve element is connected with the valve outlet member via a torsion rod. Both valve elements have longitudinal control grooves that, at least partly, are limited in terms of their axial length and that cooperate directly with each other for the control of a pressure medium to and from two working chambers of a servomotor.
2. Description of the Prior Art
Such a rotary slide valve is known, for example, from U.S. Pat. No. 3,746,045. Like other known rotary slide valves, the known rotary slide valve contains a rotary slide that is guided in an axial borehole of a control sleeve. The rotary valve is connected with a valve outlet member via a torsion rod. Besides, the rotary slide is connected with the valve outlet member via a dead-travel clutch. Such a dead-travel clutch limits the relative turning of the two valve elements toward each other and creates a mechanical stop of the valve after the turning path of the dead-travel clutch has been used up. In case the auxiliary power support fails, it must be possible to transmit the entire mechanical steering force via this mechanical stop. These operating conditions create the dimensions of the dead-travel clutch and thus of the two valve elements and the entire rotary slide valve. The outside dimensions of the rotary slide valve, which are determined by the possible high mechanical stresses, are frequently too great for the limited installation space in a motor vehicle.
The task of the invention, therefore, is to reduce the dimensions of a known rotary slide valve and to improve the steering qualities of the auxiliary power steering.